1. Field of the Invention
The present invention relates to an optical module and a manufacturing method therefor.
2. Description of the Related Art
In recent years, the development of an optical access network has been actively carried out. For realization of the optical access network, reducing the cost of an optical device and/or an optical module is a very important subject. Further, in encapsulating an optical element for making conversion from light to electricity or conversion from electricity to light, a further cost reduction is necessary, and it is required to realize an optical module which can simply encapsulate the optical element and can ensure a sufficient reliability.
In many optical modules at present, a metal package or a ceramic package is used to ensure reliability, and the package is hermetically sealed by welding or soldering, so that the cost of each optical module becomes very high. It is therefore an important subject for the cost reduction of an optical module to simplify an encapsulation method for an optical element. As an example of a method of simply hermetically sealing an optical module, there has been proposed a method including the steps of applying a resin to the entire surface of a substrate on which an optical element is mounted, and next curing the resin to hermetically seal the optical element (Mitsuo Fukuda et al., "Plastic Packaging of Semiconductor Laser Diode", Electronic Components and Conference, 1996, pp 1101-1108).
An optical module such as a light emitting module or a photodetecting module is required to be connected to an optical connector, so as to launch an optical signal to an optical fiber transmission line or to receive an optical signal from an optical fiber transmission line, and it is accordingly necessary to realize an optical module allowing the connection to the optical connector with a simple structure. However, in the case that a resin is applied to the entire surface of a substrate on which an optical element is mounted, and the resin is next cured to hermetically seal the optical element as described in the above literature, there is a possibility of separation of the resin from the substrate or generation of cracks or the like in the resin due to a difference in coefficient of linear expansion between the substrate and the resin. Furthermore, the substrate may be broken by a residual stress in the resin.